"The Helmet"




by Dr. Ken
The November article of HELMET NEWS raised a question from a reader who did not understand a statement made regarding the size of the impact area of the helmet. Our reader noted that in earlier HELMET NEWS articles about helmet safety and injuries, that I had stated that the shape of the helmet was designed to deflect contact blows and that the goal was to have the time of contact reduced as much as possible in order to protect the head and neck areas. He assumed that if contact was made with "the smallest possible area" on the helmet and then "glanced off", to use a phrase I had written, the shorter the time of contact. He was thus confused when in the November HELMET NEWS, I stated that "applied force to a smaller area, the greater the pressure; the same applied force to a larger area, the less the pressure."
If a singular pressure is applied to a helmet as the running back smashes into the line of scrimmage, we want that force to be dissipated over a large area and we want it "off of the helmet" and thus off of the involved bodyparts, as quickly as possible. The helmet's shape allows for this. In layman's terms, the force is "spread out" over a wide area. If instead, the pressure from the force that is applied to the helmet is very concentrated, the pressure transferred to the underlying bodypart is greater. While it is safest to have the smallest possible helmet strike the smallest portion of the helmet of the wearer, we want that force to be "spread out around the rest of the helmet shell" as much as possible, if that makes for an understandable statement. However, we want to avoid transferring force through the helmet and its lining in a manner that concentrates that force in a very small area of the head, for example. Again, think of a nail. The point is as small and as "sharp" as possible because this allows for the most concentration of the force of the hammer hitting it to be transferred and thus, the greatest penetration into the wood. We don't want that type of pressure directed into our heads! Thus, we have a helmet shell shape that deflects the blow and "spreads it out" as much as possible. While saying that, remember that we don't want our running back to suffer a hit to the helmet that covers a large area (picture Gene "Big Daddy" Lipscomb's helmet smashing into a sixth grader's youth model) as that would increase the chance of injury.
The helmet's ability to transfer or in our example, dissipate force, lies in part to its rigid nature which allows it to absorb the blow as a singular unit. This reduces the pressure at the point of contact, making for a "safer" hit. If the helmet shell was not rigid and did not act as a singular unit, the force would not be dissipated as well and the actual pressure of the hit, of each contact, would be more concentrated and greater with more injury causing potential. The inner lining of the helmet however, is a "different story" because we want the force to be dissipated over a longer period of time and the compression of the helmet's liner materials allows for this. That will be discussed next month in HELMET NEWS.